Structural member and method of making by cold rolling followed by induction or resistance welding

ABSTRACT

A multiple component structural member is made by cold roll forming two continuous strips of metal on opposite sides of a third continuous strip of metal. The cold rolling process creates two hollow flange elements with a continuous aperture in which the edges of the third continuous strip of metal is partly extended, followed by resistance or induction welding to create the multiple component structural member.

This invention relates to a structural member and a process forcontinuous formation of said structural members.

Processes for continuous formation of structural members are well known.U.S. Pat. No. 3,427,427, for example describes a process for formingfinned metal tubes by welding a double strip of metal helically about orlongitudinally of a tubular member and then forcing apart the adjacentstrips to form parallel helical or longitudinal cooling fins. A tubularmember having one or more transverse flanges may also be formed bywelding a double strip of metal to a planar flange member.

Reference is also made in U.S. Pat. No. 3,827,117 to a process andapparatus for forming truss members which comprise simultaneouslyforming channel members from a pair of endless strips, forming strutmembers from an endless third strip, then guiding the channels in apredetermined relation to each other with a continuous folded strutmember therebetween and thereafter welding the apices of the struts tothe channel members.

It is known in the art to form solid structural members such as I-beams,H-beams, Z-beams and T-beams wherein coils of steel are slit to width,designated as either flanges or webs and continuously fed through a highfrequency forge welding mill wherein electrical contacts induce highfrequency current which in turn creates a hot plastic metal region onthe edges of the web and in the middle of the flanges. High pressurerolls then forge the plastic regions of the steels togethermetallurgically to produce a true forged weld without the use of fillermaterials. Exemplary of this process is U.S. Pat. No 3,713,205 whichrelates to a process for producing structural members such as I- orT-beams having one or two solid flanges attached to a web.

Other methods of producing solid flange structural members are descriedin U.S. Pat. No. 3,199,174 which attaches flange strips to longitudinaledges of a web by fillet welds. U.S. Pat. Nos. 3,760,781, 3,713,205 and4,586,646 also describe similar methods of forming structural members.

Conventional solid structural members have certain disadvantages whichare described fully in Patent Specification PCT/AU89/00313 to thepresent applicant. These briefly include:

(i) high exposed surface area to mass and strength ratios which lead toincreased costs for both corrosion protection and fire proofing; and

(ii) web width to thickness ratios are generally limited to avoidreductions in section load bearing capacity due to local bucklingconsiderations and the method of manufacture leads to production ofsubstantial mill scale and rust.

The aforementioned PCT specification describes a structural memberhaving a central web and a hollow flange extending along each edgethereof. This structural member is formed continuously from a singlesheet of metal by a roll forming process. This structural member wasfound to be useful in many ways in that it simulated the strengthcharacteristics of traditional hot rolled steel structural members sucha I-beams, H-beams and RSJ's but without many of the disadvantages ofsuch traditional structural members.

Hollow flanged structural members are described in Merson U.S. Pat. No.3,342,007 and U.S. Pat. No. 1,377,251. The hollow side flanges areformed with a free edge positioned adjacent the web member but unsecuredthereto. Other relevant prior art structural members are disclosed inAustralian Design Registrations 81038, 81034, 82833 or 84401 which eachdisclosed a structural member formed from a multiplicity of separatecomponents comprising a web and a pair of hollow flange sections allmade from thin sheet material and wherein the edges of the web werereceived in the interior of each of the hollow end sections and abuttedan internal surface of same. In each of these cases the process offormation was not described and thus the hollow flange sections could bepress formed or roll formed for example. The web presumably would beattached to each hollow flange section by a spot welding process forexample and thus does not suggest the economics of a continuous processnor does it suggest the strength characteristics inherent in structuralmembers formed in accordance with the present invention.

Reference may also be made to U.S.S.R. Patent 827723 which describes aprofiled structural element similar to that described in U.S. Pat. No.3,342,007. This element is manufactured from a single sheet and has aweb and hollow flange sections wherein adjacent faces of the web andflange sections may be welded by seam welding. Each flange sectionincludes a free edge portion which extends into the confines thereof. Itis not clear from this reference whether the seam welding process iscontinuous or discontinuous but it does appear that the seam weld is afillet weld which does suggest some inherent limitations in processeconomy and structural integrity of the structural member so formed.

U.S. Pat. No. 4,562,630 describes a process for the manufacture of heatexchange elements wherein thin sheets of metal are lap welded alongspaced parallel seams defining a channel. At least one of the sheets isprovided with a longitudinally extending groove which forms the channelrecess and a liquid filler material is introduced into the thus formedcavity and allowed to solidify. The solidified filler material is usedas a supporting core while the metallic tube is subjected to plasticdeformation to achieve a desired cross sectional shape. The heatexchanger structure so formed comprises a plurality of hollow paralleltubes separated by webs.

U.S. Pat. No 4,301,348 describes a continuous method of forming squaresteel pipes from relatively thick metal plates. In this process steelplate is continuously paid off a roll and severed into lengths which aresubsequently folded to a desired cross-sectional shape. The partiallyformed hollow pipes are then tack welded end to end and then the freeedges of the section are brought together under pressure from rollers toenable a continuous seam weld by high frequency welding.

The tack welded beams are then severed at the tack weld regions to formhollow pipes of predetermined length.

While abovementioned PCT specification PCT/AU89/00313 disclosed astructural member comprising a single strip of metal roll formed toprovide a web with hollow flanges, it has been discovered that in manyinstances manufacture of a structural member by roll forming from asingle metal sheet was not desirable and sometimes it is found to bemore beneficial to roll form structural members comprising one or morewebs and two or more hollow flange sections wherein the structuralmember was formed from a multiplicity of separate components.

Some of the advantages of using a multiplicity of separate metalcomponents or strips instead of a single metal sheet or strip inrelation to manufacture of a structural member having one or more weband two or more hollow flange sections are set out hereinbelow:

(a) The process enables a different thickness of metal to be used forany or all of the web and flange sections. Thus, by varying thethickness of the web relative to the flanges this allows flexibility inthe combination of shear capacity and bending capacity of the structuralmember. The use of thicker metal in the flanges rather than in the webwill aid in the structural efficiency of the structural member inbending. Also, one of the flanges could be of thicker metal than theother flange whale still maintaining the same outside dimensions. Forspecial applications such as a composite beam where monosymmetry of thehollow flange beam section is more efficient, the external visualappearance is not altered and the reduction of member stability due tobuckling is kept to a minimum.

(b) A different strength grade of the metal may be used any or all ofthe flanges and the web. Thus, a higher strength metal in the flangesthan in the web will aid in the cost efficiency of the structural membersince the lower strength web metal is normally less expensive. Also,there may be special circumstances where one flange does not need ametal strength as high as the other flange. Use of high strength metalsmay also allow the use of thinner steel sections to achieve a reductionin overall mass.

(c) The web plate may be extended as far as is desired into the hollowflange. Extending the web plate to butt against and be welded to theinterior of the hollow flange will be of great benefit for supportingconcentrated loads on the flange.

It is an object of the present invention to provide a process forcontinuous formation of a structural member formed from a multiplicityof separate components which process may alleviate the disadvantages ofthe prior art structures and/or methods for forming same.

The invention, in one aspect provides a method of continuously forming astructural member having at least one web component and at least onehollow flange component including the steps of:

(i) guiding said at least one web component into a predeterminedabutting Juxtaposition with at least one simultaneously roll formedhollow flange component;

(ii) continuously fusing said at least one hollow flange component to arespective longitudinal edge of said at least one web component to forman integral structure; and,

(iii) subsequently severing said continuously formed structure intopredetermined lengths.

In regard to steps (i) and (ii) above, it is emphasised that these stepsinclude the situation wherein the juxtapositional orientation of thecomponents and the welding can occur separately or simultaneously in thesame or spatially separated regions in a continuous fabrication process.

The hollow flange components may be roll formed in adjacent roll formingstations associated with a single roll forming mill or alternatively thehollow flange sections may be roll formed in separate roll formingmills.

Preferably roll forming of the hollow flange components and fusion tothe one or more web components occurs in a single apparatus. Each hollowflange component and said one or more web components may be formed fromrespective coils of metal strip or from the same coil which is initiallyslit or otherwise separated into necessary precursor strip components.

Fusion of respective web and hollow flange components may be achieved ina number of ways.

The hollow flange component may be roll formed to a predetermined crosssectional shape from a flat strip of metal and its free edges are fusedtogether to form an integral hollow member before being subsequentlyfused to a longitudinal edge of a respective web component.

Alternatively, the free edges of the roll formed hollow flange componentmay be fused to opposing surfaces of the web component adjacent the edgethereof to form a closed hollow flange formed integrally with the web.

In yet a further alternative, the free edges of the roll formed hollowflange component may be fused to opposing surfaces of the web componentinwardly from an edge thereof whereby a free edge of the web extends atleast partially into the interior of said hollow flange or completelyinto the hollow flange whereby the free edge of the web member abuts aninterior surface of the hollow flange. If required, the free edge of theweb may be fused to the interior of said hollow flange to form separatecompartments therein and/or to reinforce said hollow flange.

In another embodiment structural members having at least one web and atleast one hollow flange may be formed by fusing to at least onelongitudinal edge of a generally planar web a generally planar flangestrip intermediate the longitudinal edges of the flange strip andsubsequently roll forming said flange strip to form one or more hollowflange members along said at least one longitudinal edge of said web.

The free edges of said flange strip may be deformed in a direction awayfrom said web to form a hollow flange member.

Alternatively the free edges of said flange strip may be deformed in adirection towards said web to form a hollow flange member dividedinternally by an edge portion of said web.

Suitably the free edges of the flange strip may be fused together toform a hollow flange when deformed in a direction away from the web.

Similarly, when the free edges of the flange strip are deformed in adirection towards the web, those free edges may be fused to the web toform a hollow flange with the web extending therefrom.

The structural member may be formed with hollow flanges extending alongboth sides of the web with either or both of the flange strips beingdeformed in a direction towards or away from the web.

If required, the structural member may include one hollow flange and asolid generally planar flange extending along opposite edges of saidweb.

The free edges of the flange strips on opposite sides of a web may bedeformed in a direction towards said web and adjacent free edges ofopposing flange strips may be fused together to form a hollow memberdivided by a web.

The free edges of one or more of the flange strips may be roll formed toform a flange member having hollow flange elements extendinglongitudinally thereof.

The respective hollow flanges may be formed with any suitable crosssectional shape and may be the same or different in a structural memberhaving two or more hollow flanges.

Similarly the hollow flanges may be of similar or differentcross-sectional area and may be formed from metal strips having the sameor different thickness. The web component may be planar or it may becontoured in a transverse or longitudinal direction.

The structural member may be symmetrical or asymmetrical about givenaxes.

The structural member may be generally planar in cross-sectionalconfiguration or it may be non planar in respect of adjacent webs.

Any suitable means may be employed to achieve fusion between respectiveweb and hollow flange components.

Preferably high frequency induction and/or resistance welding techniquesare employed with the present invention to facilitate high line speeds,consistency and structural integrity of welds and extreme flexibility inthe application of welds between adjacent members.

Although other welding techniques may be employed with the invention,these techniques are considered to possess one or more disadvantageswhen compared to high frequency induction or resistance weldingtechniques.

Other fusion techniques include:

(i) shielded metal arc welding (SMAW) which requires the use of fluxmaterial on a consumable electrode which vaporises to form a shieldinggas around the molten weld metal;

(ii) gas metal arc welding (GMAW) or metal inert gas welding (MIGW orMIG) which requires the use of a consumable electrode and also ashielding gas;

(iii) gas tungsten arc welding (GTAW or TIG) which requires the use of anon-consumable tungsten electrode and a filler wire fed in separately aswell as shielding gas;

(iv) flux core arc welding (FCAW) which requires the same materials asSMAW; and

(v) gas welding, e.g. oxy/acetylene.

Although these other techniques may be applicable in the fabrication ofcertain structural members according to the invention (and to thisextent fall within the scope of the invention as it may relate tocontinuous production of certain novel structural members per se) thereare a number of inherent limitations associated with the use of thesewelding techniques.

In all of the welding techniques which require the use of consumableelectrodes, it is possible only to form a fillet weld at a perpendicularJunction between adjoining metal components. In many cases, (for examplewith hollow flanges) it is possible only to form a fillet weld at theexposed side of the joint. For thick metals, the use of a single filletweld may necessitate several weld applications to obtain initialpenetration and subsequently to build up the weld thickness.

As a rule, it is difficult to control automated continuous welding withconsumable electrode welding systems to maintain a consistent standardof weld integrity. This difficulty is exacerbated when it is required toweld sections of differing thickness, particularly on a high speedmanufacturing line. Apart from the high cost of consumables such aselectrode materials and shielding gases, these techniques are generallysuitable only for welding of articles of finite length rather than in acontinuous process which would otherwise require continual replenishmentof consumables.

Generally speaking, gas welding using such gases as oxygen and acetyleneis to slow a process, difficult to automate and gives rise to severedistortion in welded articles, particularly when thin metal areemployed.

Forge welding is inappropriate to welded Joints where access to one sideonly of the joint is possible.

Accordingly, it is particularly preferred to use high frequencyelectrical induction or resistance welding according to the presentinvention to accommodate the following characteristics associates withthe present invention:

1. Continuous production

2. High line speeds

3. Maximised weld strength

4. Fluid tight integrity of weld when hollow flanges used as conduitsfor liquid and gaseous fluids.

5. Neat weld appearance with little or no post finishing except perhapsfor simultaneous scaring operation.

6. Multiple simultaneous welds with minimum stress and/or deformation.

7. Multiple components of the same or varying thickness.

8. Minimum downtime in setting up and changing over apparatus fordifferent products.

In order that the process according to the invention may be more clearlyunderstood, reference is now made to various preferred embodimentsillustrated in the accompanying drawings in which:

FIG. 1 illustrates schematically the typical stages of formation of astructural member having a central web and hollow flanges extendingalong the edges of the web.

FIG. 2 illustrates schematically one form of roll forming/weldingapparatus.

FIG. 3 is an enlarged view of the region encircled in FIG. 2.

FIG. 4 is a cross-sectional view through A--A in FIG. 3.

FIGS. 5-12 illustrate schematically the progressive contouring of thehollow side flanges in the roll mill 4 shown in broke outline in FIG. 2.

FIGS. 13-15 illustrate schematically alternative cross sectionalconfigurations at welding station 5 shown in broken outline in FIG. 2.

FIG. 16 illustrates schematically an alternative form of rollforming/welding apparatus.

FIGS. 17-37 illustrate schematically a non-exhaustive array of crosssectional shapes possible according to the present invention.

FIGS. 38 and 39 illustrate schematically an alternative method offormation of hollow flanges on a web.

FIGS. 40-47 show schematically a non exhaustive array of cross sectionalshapes according to the alternative method illustrated in FIGS. 38 and39.

In FIG. 1 each of the three plates enters the process as a planar metalstrip, the web plate perpendicular to the two flange plates as shown instage 1. The orientation of the plates, either relative to each other orglobally, need not necessarily be as shown in the diagram. It ispossible, for example, that the web plate could be in the verticalposition and the flange plates horizontal, or that all of the platesbegin in the horizontal position. It is also possible that the web plateis brought into the final position between the flanges at any stagebefore welding.

Each flange plate passes through a series of forming stations tosuccessively deform the metal strip into a substantially hollow sectionwherein the free edges are located adjacent to the web plate, as shownin stages 2 to 4. It is also possible that the web plate is subjected topreforming operations wherein ancillary or additional structuralfeatures or embellishments may be imparted to the metal strip in orderto provide benefits for the particular end use of the product. Suchadditional features may include perforation or dintouring, either in atransverse or longitudinal direction.

The free edges of the deformed flange plates (4 edges in total) are thenwelded to the web so as to form the hollow flanges (stage 5). Any typeof fusion welding is possible, but the favoured method is high frequencyelectric resistance welding.

At the welding station it is also within the scope of the process of theinvention to apply one or more scarfing operations to the workpiecewhereby weld projections or excess weld bead may be removed. As analternative to scaring to remove excess weld bead, there also may beused weld bead flattening.

Finally, the workpiece is passed through a shaping and straighteningstation wherein a series of shaping rolls are used to produce thedesired cross-sectional profile (stages 6 to 8). A series ofstraightening rolls is then used to ensure the straightness of the finalproduct. However, it is also possible to avoid the use of shaping rollsby direct forming each metal strip so that after passing through thewelding station it is already in the desired final shape.

In FIG. 2 the apparatus comprises a let off stand 1 supporting a coiledroll 2 of sheet steel, a slitting station 3, a tandem roll forming millshown generally at 4, a welding station shown generally at 5 and asevering station shown generally at 6.

As the sheet of steel 7 leaves the roll 2 it proceeds to a slittingstation 3 where the sheet 7 is slit into strips 7a, 7b and 7c ofappropriate width.

Strips 7a and 7c are slit to widths appropriate for the desired shapeand cross sectional area of hollow flanges 8a, 8c to be subsequentlyformed from those strips and strip 7b forms a web of desired width.

After slitting, strips 7a, 7b and 7c proceed to a tandem roll formingmill 4 comprising tube forming stations 4a and 4b spaced laterally oneach side of strip 7b.

Strips 7a and 7c are progressively deformed in shaping stations 9a, 9b,10a, 10b and 11a, 11b respectively to form hollow members 12a, 12brespectively of predetermined shape. The abutting free ends ofrespective strips 7a, 7c are butt welded by high frequency induction orresistance welding at welding stations 13a, 13b to form hollow tubes 8a,8c having a continuous integral wall. The tubes 8a, 8c then proceed tofinal shaping and sizing stations 14a, 14b respectively.

In the region between roll forming stations 9a, 10a, 11a, 14a and 9b,10b, 11b, 14b respectively the planar strip 7b is supported by rollers15 having horizontal axes and also by slotted rollers 16 on verticalaxes which support the edges of strip 7b.

In the region of welding station 5, the tubular members 8a, 8c and thecentral web 7b are guided into abutting relationship by rollers 17, 18and the free edges of web 7b are butt welded to the surface of tubes 8a,8c by high frequency induction or resistance welding in the presence ofnip rollers 19 which urge the members together for fusion. Scarfingcutters 20 remove any excess bead from the region of the weld.

The continuously formed integral structure 21 comprising a central weband hollow edge flanges then proceeds to a severing station 6 whereuponstructure 21 is severed into predetermined lengths by a flying saw 22.

FIG. 3 is an enlarged view of the convergence region encircled in FIG. 2showing the convergence of tubular members 8a, 8c with web 7b.

FIG. 4 is a cross sectional view through A--A in FIG. 3.

FIGS. 5-12 show schematically the progressively forming flange tubeprofiles at various roll stand positions in the roll forming mill region4 shown in broken outline in FIG. 2.

FIGS. 13-15 show schematically cross sectional views of variousweb/hollow flange welding configurations adjacent the welding station 5shown in broken outline in FIG. 2.

FIG. 16 shows schematically an alternative arrangement to that of FIG.2.

In FIG. 16 the apparatus comprises separate let-off stations 30, 31, 32each supporting separate coiled rolls 33, 34, 35 of sheet steel, each ofthe same or different thickness and width if required. Strips 36 and 38issuing from rolls 33, 35 respectively are directed to roll formingmills 39,40 to form hollow members 41, 42 respectively of predeterminedshape and cross sectional area. Unlike the system illustrated withreference to FIG. 2, the free edges of strips 36 and 38 are not weldedtogether to form a continuous wall--rather, the respective pairs of freeedges are slightly separated to form continuous slots which face arespective edge of central strip or web 37.

In the region of welding station 43 the free edges of web 37 are guidedby rollers 44 into the respective slots in adjacent hollow members 41,42 to a respective distance equal to the respective wall thicknesses ofmembers 41, 42. Nip rollers 45 compress members 41,42 to urge theirrespective free edges into contact with upper and lower surfaces of web37 immediately prior to welding by high frequency electrical inductionor resistance welding units 46. Rollers 47, 48, 49 and 50 initiallysupport web 37 and subsequently the integral structure 51.

The structure 51 is then severed into predetermined lengths by a flyingsaw (not shown) or the like.

Suitably roll forming mills 39, 40 are laterally movable to accommodatediffering widths of web 37.

A number of significant variations to the method and apparatus of theinvention to achieve a wide variety of structural members.

For example, either of the systems of FIGS. 2 or 16 may be adapted forthe welding process described in the alternative system. Further, in theprocess of welding the lips of a slotted tubular member to the opposingsurfaces of a web member, the free edge of the web member may be guidedfully into the tubular member until it engages the inner wall of thetubular member. If required the free edge of the web may be additionallywelded to the interior of the tubular member by high frequency inductionwelding to form a hollow flange divided into separate fluid tightcompartments.

In other variations the central web may include pre or post formedapertures or it may include a longitudinally or transversely extendingprofiled shape in the form of deep or shallow channels, ribs or thelike. In the case of transversely extending contoured profiles, theinwardly facing regions of opposed hollow flanges include planar facesarranged perpendicularly to the edges of the web to facilitate weldingof the components of the structural member.

Tapered structural members may be fabricated by the use of a web havingalternating inwardly and outwardly directed edges at regular andpredetermined intervals. The continuous structure so formed is severedat regions of major and minor width to form tapered structural members.

Although the various aspects of the invention have been illustrated withreference to a structural member comprising a central web having hollowside flanges, it should be appreciated that the invention is applicableto a wide variety of combinations of webs and hollow flanges. By way ofnon-limiting example, a variety of cross sectional shapes areillustrated in FIGS. 17-37 and it will be clear to a skilled addresseethat for structures formed from more than three components, appropriatemodifications and additions will be required to the systems illustratedin FIGS. 2 and 16.

It will be equally clear to a skilled addressee that in FIGS. 17-37 thehollow flanges shown schematically as circular in cross section may beof any cross sectional shape able to be produced by roll forming. Suchshapes include oval, elliptical, square, rectangular, triangular,polygonal and may be symmetrical or asymmetrical. The web and hollowflanges may be joined by the web edge or tube lip welding methodsdescribed above or a combination thereof.

It will be clear to a skilled addressee that structural members made inaccordance with the present invention may be used for a variety ofpurposes. Examples of end use may include:

Fence panels

Truss members

Truss members with integral reticulation for fire extinguishing systems.

Truss members with integral services conduits.

Reinforcing members for mine roofs and floors.

Replacement for conventional I-beams, H-beams, T-beams, Z-beams andRSJ's and like structural members.

Reinforcing members for concrete structures.

For structural applications, the wide relatively thin web sectionprovides a convenient member for attachment of support brackets,connecting members and the like. If required the structural membersaccording to the invention may be provided with one or more welded stripflanges either on a hollow flange member or on a planar web member. Theadditional strip flange may be employed as a mounting means for items tobe attached to or supported by the structural member. FIG. 32aillustrates a structural member with a strip flange.

Subsequent interconnection of selected lengths of various crosssectional shapes can give rise to unique structures. For exampleinterconnection of respective flanges of the structure shown in FIG. 32bcan give rise to a straight or tapered box section member having atubular member at each corner. Complex structures may be achieved byinterconnection of various cross-sectional shapes.

FIG. 37 illustrates a particularly effective beam structure which may beused in applications having a high resistance to torsional failure. Suchapplications may include horizontal beams and upright supports,particularly free standing pole-like members. The structure may befabricated from separate web and flange members but, as illustrated, maycomprise a first member 60 formed from a single strip of metal in afirst roll mill in accordance with the process of co-pending patentapplication number PCT/AU89/00313 (the disclosure of which isincorporated herein by cross-reference) and subsequently deformed toprovide a channel shape central web 61 with hollow flanges 62, 63.

A third hollow flange member 64 is formed in an adjacent roll formingmill and members 60 and 64 are then converged to be welded to opposingsides of web 65.

FIG. 38 illustrates schematically an alternative method of forminghollow flanges on a web of a structural member.

Although, for the sake of simplicity, the following description islimited to the formation of a single hollow flange on a web, it shouldbe understood that the process is equally applicable to the formation ofother hollow flanges in structural members comprising two or more hollowflanges.

In FIG. 38(a) a planar flange strip 70 is fused to a planar web strip 71by high frequency induction or resistance welding utilizing a modifiedform of the apparatus illustrated in FIG. 2 or FIG. 16. Alternatively,the web 71 may be fused to flange 70 by a forge welding processdescribed generally in U.S. Pat. No 3,713,205, the disclosure of whichis incorporated herein by cross-reference.

After fusing web 71 and flange 70 in a perpendicular configuration, thesides 70a, 70b of flange 70 are deformed away from web 71 in a rollforming mill to form a hollow flange member 72 with the free edges ofsides 70a, 70b being fused together by a suitable continuous weldingprocess such as high frequency electrical induction or resistancewelding.

FIGS. 38b, 38c and 38d are exemplary of hollow flange shapes which maybe obtained by this process.

FIG. 39 shows a variation on the process of FIG. 38 wherein the sides70a, 70b of flange 70 are deformed towards web 71 and the free edges ofsides 70a, 70b are fused to opposing sides of web 71, preferably by highfrequency electrical induction or resistance welding.

The hollow flange 72 so formed is divided into separate compartments 73,74 by web 71 which serves to reinforce the hollow flange 72 against thebuckling mode of failure. In this manner it is possible to employ aflange 70 of a lesser thickness or lower grade of steel that mayotherwise be required for a non reinforced hollow flange.

FIG. 40 shows a cross section of a structural member comprising a web 75and hollow flanges 76, 77 of differing size. In this example, hollowflanges 76, 77 are formed by deforming a planar flange strip away fromweb 75 as shown generally in FIG. 38.

FIG. 41 shows a variation of the structure of FIG. 40 wherein hollowflange 76 is formed by deforming a flange strip towards web 75 as showngenerally in FIG. 39.

FIGS. 42, 43 show yet another variation wherein the free edges offlanges 78, 79 are fused together to form a hollow member divided by aweb 80.

FIG. 44 shows a further variation on the structure of FIG. 42 whereinthe free edges on one side of asymmetric flanges 80, 81 are fusedtogether to form with web 82, a hollow beam 83 with longitudinallyextending solid flanges 84, 85.

FIG. 45 is a variant of the structure of FIG. 44 wherein solid flanges84, 85 are deformed towards web 82 to form hollow compartments 86, 87with the free edges of flanges 84, 85 being fused to web 82.

FIG. 46 illustrates yet another configuration of a structural memberaccording to the invention.

In this embodiment a web 90 is fused to parallel flange strips 91, 92 byforge welding or high frequency electrical induction or resistancewelding to form a member having a generally I-shaped cross section. Eachof web 91 and flange strips 91 and 92 are of differing thickness.

The free edges of flange strip 92 are then deformed away from web 90 byroll forming and the free edges thereof are fused together to form ahollow flange 93.

FIG. 47 shows an embodiment wherein a flange strip 94 is fused to web 95by forge welding or high frequency electrical induction or resistancewelding and subsequently the opposed edges of flange strip 94 are rollformed to form hollow flanges 96, 97 on opposing sides of flange strip94.

A particular advantage of the present invention over the prior art isthat the manufacturing apparatus and process is readily adaptable toaccommodate production of structural member having a wide range oflength and width dimensions as well as metal thicknesses.

Typically, metal thicknesses in the range of about 0.5 mm to 20 mm maybe employed in the process and products according to the invention.

I claim:
 1. A method for the continuous formation of a structural memberhaving at least one web element and at least one hollow flange elementextending longitudinally of an edge of said web element, said methodincluding the steps of:cold roll forming a first continuous strip ofmetal to form said at least one hollow flange element, the free edges ofwhich are spaced to form a continuous aperture therein; guiding a secondcontinuous strip of metal between said free edges and at least partiallyinto said aperture; and continuously fusing said free edges to opposedfaces of said web element by high frequency electrical induction orresistance welding.
 2. A method as claimed in claim 1 wherein a thirdcontinuous strip of metal is cold roll formed to form a further hollowflange element the free edges of which are fused to opposed faces ofsaid web element on a side thereof opposite to said first hollow flangeelement.
 3. A method as claimed in claim 2 wherein said hollow flangeelement and said further hollow flange element are cold rolled inadjacent roll forming stations associated with a single roll formingmill or in separate roll forming mills.
 4. A method as claimed in claim1 wherein the free edges of said at least one hollow flange element arefused to opposing faces of said web element adjacent a respective edgethereof, said respective edge of said web element extending at leastpartially into the interior of said at least one hollow flange element.5. A method as claimed in claim 1 wherein said respective edge of saidweb element abuts an internal surface of said at least one hollow flangeelement.
 6. A method as claimed in claim 5 wherein said respective edgeof said web element is fused to said internal surface of said at leastone hollow flange element.
 7. A method as claimed in claim 1 whereinfirst and further continuous strips of metal are cold roll formed toform respective first and further hollow flange elements, the free edgesof which are spaced to form a continuous aperture in respectiveelements;guiding the opposing edges of the second continuous strip ofmetal between the respective free edges of said first and further hollowflange elements, at least partially into respective aperturestherebetween; and continuously fusing the respective free edges of saidfirst and further flange elements to respective opposing faces of saidweb element adjacent opposed edges of said web element by high frequencyelectrical induction or resistance welding.
 8. A structural memberwhenever made in accordance with the method of claim
 1. 9. A structuralmember according to claim 8 wherein said at least one web element andsaid at least one hollow flange element are formed from metal strips ofdifferent thicknesses.
 10. A structural member according to claim 8wherein said at least one web element and said at least one hollowflange element are formed from metal strips having differentmetallurgical properties.
 11. A structural member according to claim 8including a plurality of web and/or flange elements.
 12. A structuralmember whenever made in accordance with claim 1 including a solid flangeelement extending longitudinally of said web element opposite saidhollow flange element.
 13. A method for the continuous formation of astructural member comprising at least one web element and at least onehollow flange element extending longitudinally of an edge of said webelement, said method including the steps of:continuously fusing a firstedge of a first continuous strip of metal to the surface of a secondcontinuous strip of metal intermediate the edges of said secondcontinuous strip; and subsequently cold roll forming said secondcontinuous strip to form a closed hollow flange element extendinglongitudinally of an edge of said first continuous strip, said firstcontinuous strip forming said web element.
 14. A method as claimed inclaim 13 wherein the free edges of said second continuous strip aredeformed in a direction away from said first continuous strip.
 15. Amethod as claimed in claim 14 wherein the free edges of said secondcontinuous strip are fused together to form a closed hollow flangeelement.
 16. A method as claimed in claim 14 wherein the free edges ofsaid second continuous strip are deformed in a direction towards saidfirst continuous strip.
 17. A method as claimed in claim 16 wherein thefree edges of said second continuous strip are fused to a respectiveface of said first continuous strip to form a hollow flange elementextending longitudinally of said first continuous strip, said hollowflange element being divided into separate compartments by a portion ofsaid first continuous strip.
 18. A method as claimed in claim 13 whereina third continuous strip of metal is employed to form a further hollowflange element extending along an edge of said web element opposite saidhollow flange element.